This application is a divisional of U.S. patent application Ser. No. 09/117,350, filed Jun. 9, 1999, now abandoned; which corresponds to International Application No. PCT/JP97/00188, filed Jan. 27, 1997. The entire disclosures of the above applications are hereby incorporated by reference.
The present invention is primarily used in semiconductor manufacturing facilities. More specifically, the present invention is used for supplying water when silicon dioxide film is affixed by a so-called water oxidation method (or steam oxidation method) using a process chamber.
For example, for affixing a silicon oxide film by the water oxidation method in semiconductor manufacture, high-purity water is required.
Consequently, for a conventional affixing of a silicon oxide film, as shown in FIG. 52, a process in which hydrogen gas H2 and oxygen gas O2 are allowed to combust in a quartz furnace 50 has been extensively used in which water generated by the combustion of these two gases is fed into semiconductor manufacturing equipment; and the oxide film is formed on the Si wafer surface.
In FIG. 52, numeral 51 designates a hydrogen gas nozzle, 52 a Si chip for ignition held in a vicinity of a top side of the hydrogen gas nozzle 51, and 53 is a heating lamp for heating the Si chip 52. A vicinity at a tip end of the hydrogen gas nozzle 51 inside the quartz furnace attains a high temperature from about 1800xc2x0 C. to 2000xc2x0 C. due to flames of combustion. In addition, an amount of oxygen gas O2 supplied to the quartz furnace 50 is set to a level exceeding one half that of the hydrogen gas H2 in order to completely combust the hydrogen gas H2 and to maintain safety, and flow rates of O2 and H2 are respectively separately set to several liters/min.
The process of FIG. 52 achieves excellent practical effects in that water thereby generated is of a high purity and can be instantaneously generated at a rate of several liters/min.
However, in the process of FIG. 52, there is a problem in that if the feed rate of hydrogen gas H2 or oxygen gas O2 is reduced to decrease the water amount, combustion can easily be thereby stopped and it is therefore extremely difficult to apply controls for decreasing the generated water amount, and a control range of a ratio of water to oxygen (moisture content/oxygen) is narrow.
The process has a difficulty in that because raw gas is fed directly into the reactor pipe, when combustion stops an interlock mechanism becomes indispensable to prevent explosion.
In addition, there is also a problem in that when gas flow rate is reduced, flames are generated in the vicinity of the nozzle, SiO2 composing the quartz nozzle evaporates, and these volatile materials mix in a reactor atmosphere (H2O+O2) and contaminate a gas (H2O+O2) fed to the semiconductor manufacturing equipment to such an extent that it can no longer be used for manufacturing high performance semiconductors.
In the meantime, for solving difficulties of combustion furnace type water-generating equipment as shown in FIG. 52, the inventors of this application previously developed a water generating process using the equipment shown in FIG. 53, disclosed in Japanese unexamined Patent Publication No. Hei-6-115903.
That is, this water generating process first mixes hydrogen H2, oxygen O2 and inert gas Ar to form a mixture gas C, the mixture gas C is introduced into a reaction pipe 54 made of a material having a catalytic action that can radicalize hydrogen and oxygen and at the same time the reaction pipe 54 is heated to allow hydrogen and oxygen in the mixture gas C to react, thereby generating water.
The water generating method according to the Japanese Unexamined Patent Publication No. Hei 6-115903 can obtain a mixture gas containing high-purity water ranging from low concentration on a ppb order to high concentration on a percent order, and at the same time is excellent in responsiveness, in ease of maintaining control, and in achieving high effects.
However, the water generating process using the equipment shown in FIG. 53 still has many problems that must be solved.
A first point is that because the mixture gas C of hydrogen and oxygen and argon is introduced into the reaction pipe 54, a reactivity degrades as compared with a case in which only hydrogen and oxygen are supplied, and as a result, the reactor size is increased. In particular, there is a case in which hydrogen or inert gas is added to water to adjust an oxidation-reduction power, and N2O, etc. are added to water in order to improve interface characteristics of Si and SiO2, and in such event, an increase of the reactor size results in an increase of gas consumption rate, posing a serious problem from a standpoint of economy, etc.
It is also a problem that even if hydrogen and oxygen finish the reaction completely, the product gas is a mixture gas of moisture and argon, and it is unable to output high-purity water only or a mixture gas of water and oxygen.
A second problem is a problem of responsiveness and reactivity of water generation. Because stainless pipes are used as a material having the catalytic action and catalytic action of pipe surfaces are utilized, it is unable to achieve a large reaction gas rate per unit surface area.
As result, when a large volume of generated water, for example, a water volume of about 1 liter/min., is required, the reaction pipe 54 itself is markedly increased and, at the same time, considerable time is taken to generate water.
A third problem is safety. In order to improve safety of this water-generating equipment, the invention of Japanese Unexamined Patent Publication No. Hei 6-115903 adjusts a heating temperature of the reaction pipe 54 to be between 50xc2x0 C. and 500xc2x0 C., and at the same time, the whole reaction pipe 54 is uniformly heated to the same temperature.
However, because a significant portion of the reaction between hydrogen and oxygen in the reaction pipe 54 takes place at a portion close to an inlet end of the reaction pipe 54, the temperature of the reaction pipe 54 rises more at a portion closer to the inlet end of the mixture gas due to reaction heat.
As a result, for example, if the heating temperature of the reaction pipe 54 is set to a high temperature of about 500xc2x0 C., the temperature at the reaction pipe inlet end sometimes reaches nearly about 600xc2x0 C., and even in a case of argon mixture gas, ignition of hydrogen gas may result when the argon mixture rate is small.
When the temperature of the reaction pipe 54 is lowered, there is a problem in that the reaction gas increases.
A primary object of this invention is to solve the problems in the conventional water generation process or water-generating equipment for semiconductor manufacturing equipmentxe2x80x94that is: (1) in a combustion furnace system using a quartz furnace, it is difficult to adjust the flow rate in a small flow rate region of generated water, generated water is likely to be polluted, and high-purity water cannot be obtained; (2) in a water generating process for introducing argon mixture gas into a stainless steel reaction pipe heated to a high temperature, it is unable to output water or water and oxygen mixture gas; (3) a reactor size is increased and it is difficult to downsize this equipment and at the same time, responsiveness is poor; and (4) when a heating temperature of the reactor is raised to increase reactivity and responsiveness, an inlet end temperature of the reactor rises excessively, giving rise to a danger of causing an explosion, etc.xe2x80x94, and it is another object of this invention to provide a water generating process, a water-generating reactor, a temperature control process for the water-generating reactor, and a process for forming a platinum coating catalyst layer of the water generating reactor which can greatly reduce the size of water-generating equipment and which can safely and stably produce high purity water at a rate exceeding 1 liter/min. as well as a mixture gas of high purity water and oxygen under conditions of higher responsiveness and reactivity.
That is, a water generating process of this invention basically relates to supplying hydrogen and oxygen into a reactor equipped with a material with catalytic action that can activate a reactivity of hydrogen and oxygen, and seeks to hold the reactor temperature at a level below an ignition temperature of hydrogen or gas containing hydrogen, thereby allowing the hydrogen to react with the oxygen while preventing combustion of the hydrogen and the oxygen in a process for generating water from the hydrogen and oxygen.
A first water-generating reactor according to this invention has a basic construction in which cylinders made of a material having the catalytic action that can activate the hydrogen or oxygen reactivity, or a material whose surface is covered with the same material having the catalytic action, are in a casing, to form passages through which the hydrogen and oxygen flow while coming into contact with inner and/or outer wall surfaces, there being a heater outside or inside the casing.
Furthermore, a second generating reactor according to this invention has a basic construction in which a column (filled with: granules made of a material having the catalytic action that can activate reactivity of hydrogen and/or oxygen; sintered materials of powders or fibers made of the material having the catalytic action; laminates or honeycomb bodies comprising thin sheets made of the material having the catalytic action; mesh bodies, sponge bodies, or fin-shaped bodies made of the material having the catalytic activity; or granules, sintered materials, thin sheet laminates, honeycomb bodies, mesh bodies, sponges or fin-shaped bodies whose surfaces are covered with the material having the catalytic activity) are placed, or two or more of these are placed, in the casing, and passages are formed for allowing hydrogen and oxygen to flow therethrough while coming in contact with said granules, sintered materials, laminates, honeycomb bodies, mesh bodies, or fin-shaped bodies, and, at the same time, a heater is placed outside or inside the casing.
In addition, a third water-generating reactor of this invention comprises a reactor body made of heat resistant material equipped with an inlet and water and moisture gas outlet, and a platinum coated film on an inner wall surface of the reactor body, wherein hydrogen and oxygen supplied from the inlet is brought in contact with the platinum coated film to activate the reactivity and water is produced from the hydrogen and the oxygen.
A fourth water-generating reactor according to this invention comprises a reactor body made of heat resistant material equipped with an inlet and water and moisture gas outlet, a gas diffusing member provided inside an internal space of the reactor body, and a platinum coated film provided on an inner wall surface of the reactor body, wherein hydrogen and oxygen supplied from the inlet are diffused by the gas diffusing member, are then brought into uniform contact with the platinum coated film to activate the reactivity, and water is produced from the hydrogen and the oxygen.
A process of temperature control of a water-generating reactor of this invention comprises providing a catalyst in a casing that can activate reactivity of hydrogen or oxygen, and holding an upstream-end temperature of hydrogen and oxygen under reaction in the water-generating reactor at a level lower than a downstream-end temperature in the water-generating reactor by allowing the hydrogen and oxygen to react with each other at a high temperature.
A process for forming a platinum coated catalyst of a water-generating reactor according to this invention comprises cleaning an inner wall surface of a metallic body of a reactor by applying a surface treatment, forming a barrier coating of a nonmetallic material of an oxide or a nitride on the inner wall surface and forming a platinum coated film on the barrier coating in the water-generating reactor, with the platinum coated film formed on the inner wall surface of the metallic reactor body (the body having an inlet and a water and moisture gas outlet) being used as a catalyst, with hydrogen and oxygen supplied through the inlet being brought into contact with the platinum coated film to activate their reactivity and water being generated from the hydrogen and oxygen in the water-generating reactor.
Hydrogen and oxygen, mixed at a ratio of nearly 2:1, are allowed to come into contact with the high-temperature catalyst material surface in the reactor, and radicalized by catalytic action of the catalyst material to directly react and generate water.
The generated water is guided out of an outlet end of the reactor as a steam, and thereafter, is mixed with a suitable amount of O2, N2, Ar, etc. and heated, and then supplied to the semiconductor manufacturing equipment.
Because a majority of the reactions between the hydrogen and oxygen take place in a vicinity of the gas inlet end of the reactor, in the first and the second water-generating reactors according to this invention, the inlet end of the reactor is more strongly heated by reaction heat and temperature rises greatly. Consequently, catalytic action at the reaction inlet end is weakened, gas supply position is distributed in a longitudinal direction of the reactor, or an inlet-end heater temperature is lowered so that temperature rise on the reactor inlet end is prevented.
Contrary to this, in the third and fourth water-generating reactors of this invention, because reactions of hydrogen and oxygen take place nearly uniformly throughout whole inside areas of reactor bodies, a temperature of the whole reactor body rises nearly uniformly.
In a water-generating reactor in which a platinum coating catalyst layer is formed according to this invention, the barrier film formed on the inner wall surface of the reactor body prevents metal components forming the reactor body from diffusing into the platinum coated film. Consequently, an amount of metal oxides formed in the platinum coated film greatly decreases and a high catalytic performance of platinum can, thereby, be stably maintained over a long period of time.